300 Blackout suppressed: how slow can you go?

[bellavite1]

So, I want to try to get to the lowest velocity that will reliably cycle my AR pistol.

Sort of getting 45ACP ballistics out of a 300 BLK.
Why, you ask...
I have noticed quite a difference in sound going from 1050 to 970 fps, shooting suppressed.
It obviously makes sense, less powder, less bang, no sonic crack on either one...
I'd like to try to lower it as much as 850fps with 220gr and see how quiet would it get.

The real question is:
Would the bullet (220 gr Hornady ELD-X) be stabilized at that velocity or would I risk a baffle strike?
I know a bullet will loose stability going transonic in flight, but is there a muzzle velocity below which the bullet does not stabilize?

The specs:
10.5" upper, 1:8 twist.
Suppressor is a Griffin Optimus 9 (not an actual .308, but rather a multi-cal .357).
Bullets are 220 gr Hornady ELD-X
Powder is Accurate 1680, load TBD.

[Madusa]

How low will you go? People shoot subsonic 22lr 300 yds. If you believe the longest sniper shot, it traveled 1200 yds subsonic( if you believe what they are saying they using). Ar pistol bolt slap isn’t quite. My take is if it’s slower than 600 FPS it’s artillery.

[Linkless]

Shoot a ladder test at 100 yards with no suppressor. If you start to see tumbling I'd step up quite a bit in speed to avoid it with the suppressor on. YOu may fail to cycle prior to tumbling. If that is the case you will want to retest with the suppressor as it will likely cycle at a lower powder charge than without.